Fix problem with trivial links not getting lindelays. In the case that
a 100Mb link is mapped to a trivial link, a linkdelay has to be inserted since the actual loopback bandwidth is much higher. The problem is that unlike other delays where requires_delay() will return true, this decision has to wait until after assign does the mapping and we find out that a link was mapped to a trivial link. When this happens, I insert a linkdelay "on the fly" when processing the link statements from assign.